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Figure 26-11
Forced expiratory spirograms before (A)
and after (B) bronchodilator therapy. Notice that
the forced vital capacity (FVC) is increased in B,
but flow over its midportion (FEF25%–75%
) is decreased unless adjusted
to the same volume (i.e., the portion of the FVC below total lung capacity [TLC]).
The artifact results from the increased FVC as a result of bronchodilation. If
FEF25%–75%
is measured over the same volume segment as in A,
the value increases.
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